A heater of $220\, V$ heats a volume of water in $5\,\min$ time. A heater of $110\, V$ heats the same volume of water in ............... $min$

Heater of electric kettle is made of a wire of length $L$ and diameter $d$. It takes $4$ minutes to raise the temperature of $0.5 \ kg$ water by $40\ K$. This heater is replaced by a new heater having two wires of the same material, each of length $L$ and diameter $2 d$. The way these wires are connected is given in the options. How much time in minutes will it take to raise the temperature of the same amount of water by $40K$ ?

$(A)$ $4$ if wires are in parallel

$(B)$ $2$ if wires are in series

$(C)$ $1$ if wires are in series

$(D)$ $0.5$ if wires are in parallel.

An electric bulb rated $50 \mathrm{~W}-200 \mathrm{~V}$ is connected across a $100 \mathrm{~V}$ supply. The power dissipation of the bulb is :

The $H$ amount of thermal energy is developed by a resistor in $10\,s$ when a current of $4\,A$ is passed through it. If the current is increased to $16\,A$, the thermal energy developed by the resistor in $10\,s$ will be $........\,H$

$A$ total charge $Q$ flows across a resistor $R$ during a time interval $= T$ in such a way that the current vs. time graph for $0 \rightarrow T$ is like the loop of a sin curve in the range $0 \rightarrow \pi$ . The total heat generated in the resistor is

From where electrical power derive ? Explain it.